Abstract: Au film which was used as immunoassay substrate was modified by 16-mercaptohexadecanoic acid(16-MHA) via self-assembled monolayer(SAM) technology. A sandwich assay which contains captured antibodies, antigens and labeled immuno-colloids was formed. Two different Raman reporter molecules(4,4'-bipyridine and thiophenol), which served as respective labels for each type of antibodies, were selected. SERS has the advantage of a small line width of Raman bands and high sensibility. The presence of dual-analyte was established by distinguishing the corresponding labeled reporter's Raman spectrum. By chosing suitable Raman reporter molecules and immuno-colloids of certain size, detection limit ranges from 1 to 100 fg/mL were achieved.

Key words: Surface enhanced Raman spectroscopy(SERS), Labeled immunoassay, Dual-analyte, Detection limit